It is known that laser self-mixing interference (SMI) can be used for speed and distance measurements, see G. Giuliani, M. Norgia, S. Donati, T. Bosch “Laser Diode Self-mixing Technique for Sensing Applications” in Journal of Pure and Applied Optics, 6 (2002), page 283-294. It is also known that vertical cavity surface emitting laser (VCSEL) with integrated photodiode is particularly suitable for SMI sensing applications. However, a general problem with speed measurements using self-mixing sensors is that the orientation of the sensor with respect to the road directly influences the measurement. As the vehicle frequently changes its orientation with respect to the road, e.g., due to a declination of the vehicle body induced by centrifugal forces in a curve, measurement errors are induced. Thus, the absolute measurement accuracy of a self-mixing ground speed sensor is compromised by vehicle dynamics, namely, roll and pitch movement of vehicles.